The standard-setting organization 3GPP (3rd Generation Partnership Project) is discussing Evolved Universal Terrestrial Radio Access (hereinafter, EUTRA) evolved from the third generation mobile communication method and an advanced version thereof, i.e., Advanced EUTRA (also referred to as LTE-Advanced) (Nonpatent Document 1).
In Advanced EUTRA, carrier aggregation is proposed as a technique enabling higher-speed data transmission while maintaining the compatibility with EUTRA (e.g., Nonpatent Documents 2 and 3). The carrier aggregation is a technique for improving a data rate by preparing a receiving apparatus that includes one receiver having a reception bandwidth exceeding a maximum transmission bandwidth of a transmitting apparatus or a plurality of receivers having a reception bandwidth equal to the maximum transmission bandwidth of the transmitting apparatus or exceeding the transmission bandwidth and by receiving the data of the transmitting apparatus transmitted from a plurality of different frequency bands (carrier frequencies) with the respective receivers corresponding to the different frequency bands in the receiving apparatus. Hereinafter, a receiving apparatus and a transmitting apparatus in downlink transmission will be referred to as a mobile station apparatus and a base station apparatus, respectively, and a receiving apparatus and a transmitting apparatus in uplink transmission will be referred to as a base station apparatus and a mobile station apparatus, respectively; however, the applicable range of the present invention is not necessarily limited to these apparatuses.
A mobile station apparatus of EUTRA determines whether a currently communicating base station apparatus is appropriate as a communication destination by detecting a radio link problem in a higher layer (Nonpatent Document 4, Section 5.3.11). The radio link problem is a problem generated in a lower layer (a physical layer problem in a physical layer or a random access problem in a data link layer). The physical layer problem is detected in the physical layer by comparing reception quality of a transmission signal from the base station apparatus with a threshold value. A random access problem is detected by MAC (medium access control) of the data link layer if the number of preamble transmissions reaches the maximum number of transmissions.